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My 2003 Odyssey EX AC and fan stopped working except when the fan speed was turned to max. After researching these forums I found that it was likely a bad blower motor transistor. I replaced the transistor tonight and now the AC and fan work when set to speeds other than max, but the fan will not shut off even when the climate system is turned to off.

The fan seems to operate at only the higher speeds, though it will adjust slightly as the temp control is moved up and down. The mixer valve seems to be working correctly and the air temp will change appropriately based on the set point. All this relates to the front fan. The rear units seems to be working correctly.

Any thoughts on why the fan only seems to run near max speed regardless of the setting, even when the system is turned off?
 

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Discussion Starter · #2 ·
Rereading my post, I see an important typo. What I meant to say is that the fan will NOT shut off, even when I turn the climate system off.
 

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Discussion Starter · #4 ·
Yes, I replaced the transistor assembly under the dash on the passenger side. The fan now operates on settings other than MAX but it does not seem to drop to low speed and it will not turn off.

The other symptom I'm seeing is that the A/C compressor only comes one when the temp control dial is at the lowest setting. When the A/C does kick in, the fan speed steps up. I'm not seeing anything abnormal when I run the self-diagnostic (holding "auto" and "mode" while starting the car).

I'm leaning towards the controller being bad since the system does not turn off, but I'm hoping that there is a cheaper explanation.
 

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Discussion Starter · #6 ·
It doesn't matter if it is set to AUTO, FULL AUTO, or a manual setting; the fan runs at full speed all the time. Even if I switch the climate control system off the fan continues to run at full speed.

If I turn the temp control all the way down (60) then the A/C compressor will kick in, but that is the only way the A/C will run. Last night I verified that all of the fuses have good continuity and the relays seem to be working OK.

I read another post this afternoon with similar systems that leads me to believe that either I got a bad replacement transistor, not unheard of, or the control unit is bad.

When I check the DTCs on the climate control, the LCD alternates between 88 and the lower horizontal segment on the right hand eight. So far I have not been able to figure out what that means or if it helps me in any way.

Right now I am leaning towards the CCU being bad (that's what the service writer at my dealer thinks) but I don't want to drop that much money on a part unless I am sure that it will resolve the issue.
 

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Discussion Starter · #9 ·
I like the way you think, dvpatel! That is actually exactly why I dropped into the dealer today. Unfortunately they were not interested in helping, though they were more than willing to have one of their mechanics test it for me at their going rate. They were also very willing to sell me the parts with just one catch; no returns on electrical components.

There are other dealers though. I'll have to remember that next time I am in the market for a new car or some service.

Tomorrow I am going to try the light bulb test pjigar talks about in this thread: Climate Control Trouble - Won't Report DTCs

If that is inconclusive then I will repair the old transistor assembly and see what happens before going the CCU route.
 
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